GB550255A - Improvements in and relating to dynamo electric machines - Google Patents

Abstract

550,255. Inductor-alternators. BRITISH THOMSON-HOUSTON CO., Ltd., and BARWICK, E. C. June 30, 1941, No. 8231. [Class 35] A heteropolar inductor alternator has at least one generating coil whose sides lie in excitation fields having opposite directions. It is shown that this results in a saving in coils required for a given output voltage and leaves slots for the exciting coils entirely free so that the exciting turns can be increased. In one form a generating coil 1, Fig. 2 (Prov.), is wound round two armature slots so as to bridge oppositely excited poles 2 ; the remaining coils are wound round alternate slots. If the winding is of the kind with coils wound round each slot and reversely connected, a double-pitch coil occurs at each end of a pole. If the number of slots per pole is reduced to two, the windings will be entirely double-pitch coils, as shown in Fig. 2. In these examples the slots are twice the number of rotor teeth. The ratio of slot to tooth pitch may be non-integral so that the long coils are not exactly double the pitch of the short ones; Fig. 3 shows a twophase modification with 1 6/7 slots per pole per phase, in which the long coils are 1¥ times the pitch of the short ones. The slots containing the exciting coils are indicated by dotted lines 3. The separate phases are shown in full and dotted lines and the rotor teeth are indicated at 4.